Modified spiral seam arrangement

ABSTRACT

A seam arrangement for connecting the two ends of a fabric so as to form an endless belt, particularly for use in papermaking. The seam arrangement comprises two endless coils ( 10 ) which are respectively located at the free ends of the fabric and on interdigitation are brought into union by a pintle wire. Each loop of the coils ( 10 ) is secured by a “short” fabric loop ( 22 ) and a “long” fabric loop ( 18 ). The short fabric loop is located at the right hand side of the long fabric loop when looking up the fabric towards the seam.

This invention relates to a modified spiral seam arrangement.

Spiral seams are used for example to connect the ends of fabrics to formendless belts for use in paper machine clothing, especially press feltbase cloths or dryer fabrics.

In a spiral seam, the ends of a fabric are provided at each edge to beformed with a loop structure capable of interdigitating with acorresponding loop structure on the opposite edge, and the seam isusually secured by means of a pintle wire or rod extending axiallythrough the interdigitated loops. Conveniently, the loops are providedby means of a pair of, preferably flattened, helical coils, each formedfrom a single continuous metal wire, plastic coated wire, or suitableplastic monofilament. The helical coils are woven into the fabric, orotherwise secured depending upon the nature of the substrate. One sideof the spiral is substantially flatter than the other so that the loopsare substantially D shaped, the flatter sides being directed towards thepaper supporting surface of the fabric in plan view, from the morecurved side, each loop of the spiral has an N-shape.

Machine direction (MD) warp yarns are woven in repeat groups of four toeach turn of the helical coil. Alternate yarns run short, and theremaining spaced yarns extend into the fringed area and are loopedaround the leg of the coil adjacent the seam, and a return portion ofeach is back woven into the fabric in the space made available by theyarns which have run short to in effect provide a continuous warp path.

The weave pattern is such that one of the MD yarns forms a “long”fabricloop, floated over at least the last cross machine weft yarn, and theother a “short”fabric loop coming from below the last weft yarn orfloated over fewer yarns than the “long” fabric loop. In the knownfabric seam the “short” fabric loop lies between the diagonal and theleft hand vertical limb of the N-shape of the spiral coil loop. In thisarrangement the “short” fabric loop distorts the coil loop to such anextent that part of the seam moves proud of the belt. This results inundesirable marking of the paper which is being manufactured on thebelt.

According to the present invention there is provided a seam arrangementfor connecting the ends of a fabric so as to form an endless belt, theseam arrangement comprising a first coil provided at one of said ends ofthe fabric and a second coil provided at the other of said ends of thefabric, wherein the two coils are operable to be interdigitated andsecured together by means of a pintle wire which may be passed throughthe interdigitated coil loops, and wherein two machine direction yarnsof the fabric are passed through each loop of a coil so as to secure thecoil to the fabric edge, the machine direction yarns associated witheach coil loop providing a “long” fabric loop and a “short” fabric loop,characterised in that each coil loop notionally forms an N-shape withthe top of the N-shape being provided by the free ends of the coil loopwhich are remote from the fabric end to which that coil loop is secured,and in that the “short” fabric loop lies between the “lon” fabric loopand the right hand limb of the N-shape of the spiral coil loop.

Space for back-weaving the MD yarns is created by terminating selectedMD yarns short of the edge region, at a joining point, and the returnportions back woven to the joining point so that there is no perceptiblebreak in the weave. The MD yarns would preferably be warp yarns.

It has been found that an arrangement of this kind allows the spiralcoil to be seated closer into the plane of the fabric, so that the coilstands less proud and thus reduces the extent or depth of any embossingor marking inflicted by the coil on paper which is supported on thefabric and the less proud configuration of the seam makes it less proneto wear.

An embodiment of the invention will now be briefly described withreference to the accompanying drawings wherein:

FIG. 1 is a sectional weave diagram of a seam of a known form of helicalseam;

FIG. 2 is a diagrammatic plan view showing the weave of the seam of FIG.1 from above;

FIG. 3 is a diagram corresponding to FIG. 1 showing the weave of a seamaccording to the invention; and

FIG. 4 is a diagrammatic plan view, similar to FIG. 2 of the seam ofFIG. 3.

In a prior art spiral seam, as illustrated diagrammatically in FIGS. 1and 2, a flattened helical coil member 10 has a large number of turns,each having a leg 11, alongside the edge of the woven fabric. The coil10 is flatter on its upperside 10 a, than on its lower side 10 b, thusproviding a ‘D’ shaped outline. In plan (as seen from FIG. 2) each loophas the shape of an ‘N’ with the lower side parts 10 b forming thediagonal of the N-shape. In the example, the fabric comprises two layersof cross-machine direction weft yarns, 12, with an upper layer and alower layer of staggered yams. Machine direction warp yarns 14 are woventhrough the weft yarns 12 in a pattern wherein each warp yarn floatsover two weft yarns in the upper layer, and passes under one weft yam inthe lower layer in each repeat.

The seam is formed with two MD yarns for each turn of the coil member10, a first MD yarn 16, shown in FIG. 1 as a continuous double line, hasa main part 19 which forms a “long” fabric loop 18, over the last twoupper layer cross-machine yarns and under and around the leg 11 of thecoil adjacent the fabric edge. The yams nest in the ‘V’ between thenearer end of each coil upper side 10 a and lower side 10 b, with the“short” fabric loop 22 nesting on the apex of the ‘V’ and the “long”fabric loop 18 further out on the part 10 b. The return section 17 ofthe MD yarn 16 passes over the leg 11, and then passes over the upperyarn adjacent the seam, and is back woven into the fabric for a fewrepeats. The weave space is filled by a normal MD yarn, which is cutshort to terminate adjacent the woven back end of section 17. (This isnot shown in the drawings).

A second MD yarn 20 has a main part 21 which forms a “short” fabric loop22, as it emerges from below the last bottom layer cross-machine yarnand below the last upper layer yarn to pass under and around the leg 11,adjacent the “long” fabric loop 18. After it passes about the leg 11 ofthe spiral yam 20 forms a return portion 23 which passes over the lastcross-machine yarn and is then woven back into the fabric for severalrepeats. As with the woven-back end 19 of yarn 16, the space for this isprovided by cutting short a normal MD yarn.

As can best be seen from FIG. 2, the return portions 17, 23 of yams 16,20 are located alternatingly with the main portions, the sequence fromtop to bottom of the figure being: main part 21 of yarn 20 (short fabricloop); return part 23 of yarn 20; main part 19 of yarn 16 (long fabricloop); return part 17 of yarn 16.

The fabric loops 18,22 pass about the lower part 10 b of the spiral.

It can be seen from FIG. 2 that the “short” fabric loop distorts theN-shape of the coil loop, forcing the diagonal 11 upwards in a directionperpendicular to the plane of the fabric, resulting in a proud seam.When viewed from above the N-shape can be seen to be significantlydistorted. The “long” fabric loop is consequently less tightly boundaround the diagonal and consequently it contributes less to seamstrength.

FIGS. 3 and 4 illustrate the weave pattern of a spiral seam arrangementaccording to the invention. The arrangement of cross-machine directionweft yams 32 is the same as that of FIG. 1—upper and lower layers withthe yarns staggered, and a helical coil member 30 which is of the sameconfiguration as that of FIG. 1 with more flattened upper parts 30 a andmore bowed lower parts 30 b, appearing in plan view as an ‘N’ shape. Themachine direction warp yarns 34 are again woven through the weft yarns32 in a pattern wherein each warp yarn floats over two weft yarns in theupper layer, and passes below one weft yarn in the lower layer in eachrepeat.

The seam is formed with two MD warp yarns for each turn of the coilmember 30. A first MD yarn 36, shown in FIG. 3 is a continuous doubleline, has a main part 39 which forms a “short” fabric loop 38, passingbelow the last cross-machine yarn of the upper layer and under the lastcross-machine yam of the lower layer, about the part 30 b, and thenreturns below the last two cross-machine yams of the upper layer, toform a return portion 37 which is back woven into the fabric for severalrepeats. The weave space is created by ending a normal MD yam toterminate in a joining zone with the end of woven-back portion 37. (Thisis not shown in the drawing).

A second MD yarn 40 is shown in FIG. 3 as a dashed broken line, and hasa main part 43 which forms a “long” fabric loop 42 which passes over thelast two upper layer cross-machine yarns, about the part 30 b of thecoil, and passes over the coil, to form a return portion 41, whichpasses over the last cross-machine yarn, to be woven back into thefabric for several repeats. As FIG. 4 shows, the arrangement of the mainand return yarn portions is different from that shown in FIG. 2.

The FIG. 4 arrangement in practice has the effect that the spiral isless distorted by its connection with the fabric ends and is seatedbetter into the plane of the fabric, thus reducing marking of any papersupported on the fabric. The seam stands less proud and is also lessprone to wear than previous seams. The seam achieves a far stronger seamwith respect to the length direction of the fabric and the coil is lessprone to rotating, so that interdigitation of the two opposed loopstructures during fabric seaming is made easier.

It is to be understood that the embodiment described with reference toFIGS. 3 and 4 is by way of illustration only. Many modifications andvariations are possible.

What is claimed is:
 1. A seam arrangement for connecting the ends of afabric so as to form an endless belt, the seam arrangement comprising afirst coil provided at one of said ends of the fabric and a second coilprovided at the other of said ends of the fabric, wherein the two coilsare operable to be interdigitated and secured together by means of apintle wire which may be passed through the interdigitated coil loops,and wherein two machine direction yarns of the fabric are passed througheach loop of a coil so as to secure the coil to the fabric end, themachine direction yarns associated with each coil loop providing a“long” fabric loop and a “short” fabric loop, characterised in that eachcoil loop notionally forms an N-shape, with the top of the N-shape beingprovided by free ends of the coil loop which are remote from the fabricend to which that coil loop is secured, and in that the “short” fabricloop lies between the “long” fabric loop and a right hand limb of theN-shape of the coil loop.
 2. A modified spiral seam arrangement asclaimed in claim 1, wherein a number of machine direction yarns areterminated short of the fabric end, at a joining point, and a returnportion back woven to the joining point.